How to Fix a Leaking Lawn Mower Tire Rim

This project explains how to fix a leak between the wheel rim and tire bead on a lawn mower tire. The tubeless tire on my zero turn riding mower had a slow air leak. I finally got tired (pun intended) of adding air every two weeks and decided to fix the leak once and for all.

Tubeless Lawn Mower Tire with Tire Rim Leak

How to Fix a Leaking Lawn Mower Tire Rim

The tire must be removed to locate the source of the air leak by placing it in a bucket of water and looking for bubbles. After propping up the front of the mower on some sturdy blocks to get the tire off the ground, the axle bolt is removed with two 3/4″ socket wrenches. Two wrenches are required: one to hold the bolt head and another to remove the lock nut. A box-end wrench will also do fine, but a socket wrench is quicker:

Remove the Lawnmower Tire Axle Bolt

The wheel will drop free from the caster after removing the axle bolt:

Lawnmower Wheel Removal: Axel Bolt and Bushing

The axle bolt rides inside a greased bushing and the bushing will slip out of the wheel if the tire is tilted, so best to remove it to avoid a grease stain on the floor.

Leaking Tire – Water Bucket Leak Finder

The tire is cleaned of dirt and grass clippings so as not to muddy the water. The tire is filled with compressed air to bring it up to full pressure then placed in a bucket of water filled to just below the axle – best not get water in the bearings. The tire is slowly rotated to look for bubbles indicating an air leak:

Tire in Bucket of Water to Find the Air Leak

I didn’t find any leaks in the tire face or sidewall, but there are several leaks between the wheel rim and tire bead. The bead is the part of the tire that contacts the rim. Four rim/bead leaks are seen in the video below:

One slow stream of small bubbles near the water line.

One slow stream stream of larger bubbles at the 1st blue pen mark.

Two fast streams of bubbles at the 2nd pen mark.

An alternate way for locating an air leak is to spray soapy water on the tire and looking for soap bubbles indicating an air leak. This is convenient if you don’t want to remove the tire or if a large enough bucket isn’t available. However, the underwater method is the surest way to find even the smallest air leak. On occasion, I’ve even used the bathtub to check a large diameter tire for leaks, for example a 26″ bicycle tire.

Tire Bead Sealer

Tire Bead Sealer is a thick fast drying rubber compound that’s painted on the tire bead and wheel rim to fill small imperfections and make an air tight seal. While bead sealer isn’t a glue, it does have has adhesive properties and can make the tire harder to remove from the wheel rim.

I purchased a quart can of bead sealer from NAPA auto parts (many brands are available) and used the following tools to repair the lawn mower tire:

Pencil tire pressure gauge

Tire valve core removal tool

Air blow gun with a rubber tip

Air tire chuck for inflating tires

Portable electric air compressor (not shown)

Wire brush (not shown)

Tire Bead Sealant and Air Tools

Deflate the Tire

The tire must be deflated to relieve the air pressure that presses the tire bead to the wheel rim. Hold the deflation pin of the tire gauge against the Schrader valve as shown until no more air comes out.

Deflate the Tire

Remove the Schrader Valve Core

The tire valve core should be removed to ensure there is no residual air pressure in the tire and allow for “bead breaking” in the following steps without building up pressure in the tire. The valve core removal tool has a slotted head and hollow tip that fits over the valve core to unscrew it from the valve stem. Remember: “Lefty Loosey, Righty Tighty” when unscrewing the valve core.

Tire Valve Core Removal Tool

After unscrewing the valve core, pull it out of the valve stem with your fingers. Put the valve core aside in a safe and clean place. It’s small and easy to lose.

Schrader Valve Core Removed from Tire

With the valve core removed, the tire will “breathe” freely as the tire is worked to break to the bead.

Break the Tire Bead

The tire bead bonds to the wheel rim over time due to the tire rubber adhesion, rust and dirt buildup. The bond must be broken to clean the rim and bead before applying bead sealer.

You can work all day if you don’t know the correct way to break a tire bead. A garage will have a tire bead breaking tool, but since I rarely have a need for one, a simple way is to use a 6 foot long 2×4 placed under the work bench as a lever on a wood block as shown:

Break the Tire Bead with a Simple 2×4 Lever and Block

The 2×4 lever and 2×2 block made simple work of breaking the tire bead:

Breaking a Tire Bead with a 2×4 Level and Block

The 2×4 lever and 2×2 block were random pieces of wood I had lying around my workshop and worked perfectly for breaking the tire bead:

2×4 Lever and Wood Block Tire Bead Breaker

Flip the tire over and break the bead on the other side.

Clean the Wheel Rim and Tire Bead

There was dirt, a few bits of grass, paint chips and rust between the wheel rim and tire bead. I cleaned the rim and bead with a brass wire brush (brass is softer than steel) and wiped it down with a cotton rag. This took several passes to get it clean.

Share this:

6 Comments

I had the same leak in the edge of the rim and used a small ball peen hammer and tapped in that area until the bubbles stopped. It has been leak free since. Never heard of beal seal, so will try that in the future if tapping doesn’t work. Great article!

Thanks Bob. Quite a common sense way to save me $20 or so. I used some spray electrical tape I found to be less manageable than the brush on kind. It put pretty black spots on the garage ceiling when it popped. The ones on my arm lasted 2 days. :P

Remove the valve stem core and inflate it with a rubber tipped blow gun nozzle. That should rapidly push a large enough air volume to balloon the tire and seat it against the rim. Reinstall the valve core and inflate with the air chuck.